Methods and instrumentation for positioning implants in spinal disc space in an anterior lateral approach

ABSTRACT

Instruments and methods are provided for positioning one or more implants into a spinal disc space. The instruments and methods have application in an anterior lateral approach to the disc space between the L4 and L5 vertebrae. The instruments include a distractor, a housing, a guide member to facilitate positioning of the housing, and a partition member engageable to the housing to facilitate positioning of one or more implants into the disc space.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.10/405,816, filed Apr. 2, 2003, and issuing as U.S. Pat. No. 7,326,216,which application is incorporated herein by reference in its entirety.

BACKGROUND

Access to the disc space between the L4 and L5 vertebrae can beobstructed or difficult due to anatomical considerations. For example,an anterior approach or an anterior oblique approach requires thesurgeon to retract or move, or at least work adjacent to, the majorvessels extending along the anterior portion of the spinal column. Whilean anterior oblique approach may reduce or eliminate the requirement forretraction of these major vessels, access for positioning instrumentsand implants in the posterior portion of the disc space on the side ofthe approach can be limited. Further, the instruments can still beadjacent the major vessels during the surgery.

A lateral approach to the disc space anterior of the posterior elementscan avoid the major vessels and provide access for disc spacepreparation and implant insertion, but other anatomical obstructions canbe encountered. For example, positioning instruments and implants in thespinal disc space between the L4 and L5 vertebrae from an anteriorlateral approach can be obstructed or inhibited by the iliac crest.Instrumentation and methods which facilitate placement of implants inthe spinal disc space from an anterior lateral approach are needed tomake such procedures a more viable alternative for treatment andcorrection of spinal deformities.

SUMMARY

Instruments and methods are provided for positioning one or moreimplants into a spinal disc space. The instruments and methods haveapplication in an anterior lateral approach to the disc space betweenthe L4 and L5 vertebrae. The instruments and methods can also haveapplication in other approaches to the spine at any level of the spine.

According to one aspect, instruments are provided that include adistractor, a housing, a guide member to facilitate positioning of thehousing, and a partition member engageable to the housing to facilitatepositioning of one or more implants into the disc space.

According to another aspect, a surgical instrument insertable in aspinal disc space between an upper vertebra and a lower vertebra isprovided. The instrument comprises a head including an upper surface andan opposite lower surface positionable adjacent endplates of the upperand lower vertebrae, respectively. The head defines a disc spacedistraction height between the upper and lower surfaces. A shaft extendsproximally from the head. The shaft includes a distal portion, aproximal portion, and an offset portion therebetween. The distal portionincludes a guide portion adjacent the head. The head and the guideportion extend along a first axis and the offset portion extendsproximally from the guide portion along a second axis oriented at afirst angle relative to the first axis.

According to a further aspect, a surgical instrument assembly providesaccess to a spinal disc space. The assembly comprises a distractor, ahousing and a guide instrument. The distractor includes a headpositionable in a spinal disc space and a shaft extending proximallyfrom the head. The shaft includes a guide portion along at least aportion thereof adjacent the head. The guide instrument includes a shaftand a guide member at a distal end of the shaft. The guide member isremovably engaged to the housing and moveable along the guide portion ofthe distractor with the shaft of the guide instrument adjacent to theshaft of the distractor to guide the housing along the distractor to thespinal disc space when the head is positioned in the spinal disc space.

According to another aspect, an instrument assembly for facilitatingplacement of an implant in a spinal disc space includes a housing and apartition member. The housing includes a frame member defining anopening therethrough between side walls of the housing. The housing ispositionable adjacent to the spinal disc space and provides accessthereto through the opening. The partition member is engageable to theframe in the opening. The partition member includes an extensionextending distally from the frame and positionable in the spinal discspace. The partition member is movable relative to the frame between theside walls.

According to another aspect, a surgical instrument assembly is provided.The assembly includes a body with a portion positionable in a spinaldisc space and a mounting member extending from the body. The assemblyalso includes a shaft assembly removably engageable to the mountingmember. The shaft assembly includes an outer shaft defining a distallyopening receptacle and an inner shaft movable relative to the outershaft and extending distally therefrom. The inner shaft includes adistal engagement member engageable to the mounting member. Movement ofthe engagement member relative to the outer shaft to position themounting member in the receptacle secures the body to the shaftassembly.

According to a further aspect, a method for positioning an implant in aspinal disc space of a patient comprises: accessing the spinal discspace between L4 and L5 vertebrae from a lateral approach to thepatient; and positioning a distractor in the spinal disc space with ashaft of the distractor oriented laterally to the patient, the shaftcomprising a distal portion extending laterally from the spinal discspace and a proximal portion offset relative to the distal portionanteriorly of the iliac crest.

According to another aspect, a method for positioning a spinal implantin a spinal disc space of a patient comprises: positioning a housingadjacent the disc space between the L4 and L5 vertebrae in an anteriorlateral approach; positioning a partition member through the housinginto the disc space; positioning an implant in the disc space anteriorof the partition member; and moving the partition member anteriorly tomove the implant anteriorly in the spinal disc space.

These and other aspects are also discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anterior elevation view of a sacro-lumbar segment of thespinal column.

FIG. 2 is a perspective view of a disc space distractor.

FIG. 3 is a section view of the distractor of FIG. 2 along line 3-3.

FIG. 4 is a perspective view of a housing.

FIG. 5 is a perspective view of a guide instrument attachable to thehousing of FIG. 4.

FIG. 6 is an elevation view of a portion of the guide instrument of FIG.5.

FIG. 7 is an enlarged perspective view of a guide member at the distalend of the guide instrument of FIG. 5.

FIG. 8 is a perspective view of a housing insertion instrument assemblycomprising the distractor of FIG. 3, the housing of FIG. 4 and the guideinstrument of FIG. 5.

FIG. 9 is a perspective view of a partition member.

FIG. 10 is a perspective view of an implant insertion instrumentassembly comprising the housing of FIG. 4 and the partition member ofFIG. 9.

FIG. 11 is an elevation view of a shaft assembly comprising a portion ofthe implant insertion instrument assembly.

FIG. 12 is a perspective view of a wedge displacer instrument.

FIG. 13 is a perspective view of a second displacer instrument.

FIG. 14 is perspective view looking down on the distal end portion ofthe assembly of FIG. 8 positioned adjacent a lower vertebra of a spinalcolumn segment with the distractor in the spinal disc space and thehousing being positioned with the guide instrument to provide access tothe spinal disc space.

FIG. 15 is a perspective view of the distal end portion of the assemblyof FIG. 10 looking up through the endplate of the lower vertebra of FIG.14.

FIG. 16 is a perspective view of the assembly of FIG. 10 with an implantpositioned in the spinal disc space along an anterior side of thepartition member.

FIG. 17 is a perspective of the assembly of FIG. 10 with the wedgedisplacer instrument being inserted for positioning along the posteriorside of the partition member.

FIG. 18 is a perspective of the assembly of FIG. 10 with the seconddisplacer instrument positioned in the disc space along posterior sideof the partition member.

FIG. 19 is a perspective view of the spinal disc space withmedial-laterally oriented anterior and posterior implants positionedtherein.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described embodiments, and any further applications of theprinciples of the invention as described herein are contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

Referring to FIG. 1, there is shown a spinal column segment 10 thatincludes a sacrum 12, an L5 vertebra 14, an L4 vertebra 16, and a discspace 18 between L5 vertebra 14 and L4 vertebra 16. The presentinvention provides methods and instrumentation adapted for positioningspinal implants in disc space 18 from an anterior lateral approach thatavoid or minimize the obstruction of iliac crest 20 into an accesspathway to disc space 18. The instruments and methods provide anteriorlateral access to the disc space for endplate preparation and implantinsertion into disc space 18 to support of the adjacent vertebrae withone or more medial-laterally oriented implants.

In surgical procedures for accessing disc space 18, it can be desirableto approach disc space 18 from a lateral approach along the anteriorside of iliac crest 20. With such an anterior lateral approach, themajor arteries and veins along the anterior portion of the spine can beavoided. Furthermore, the posterior neural elements, musculature, andbony structures can be avoided. With the anterior lateral approach, oneor more implants can be positioned in disc space 18 in such a mannerthat the load of the spinal column transmitted by the implants is evenlydistributed about the central axis of the spinal column. However, iliaccrest 20, particularly along its outer margin 22, can extend anteriorlyrelative to disc space 18 such that anterior lateral access to discspace 18 is impeded thereby.

Referring now to FIG. 2, there is shown a disc space distractor 30including a distal head 32 and a shaft 34 extending proximallytherefrom. Head 32 can include a first vertebral endplate surface 46 andan opposite second vertebral endplate surface 48. First and second sidesurfaces 47, 49 extend between first and second vertebral endplatesurfaces 46, 48. First and second vertebral endplate surfaces 46, 48 canbe spaced from one another to contact the adjacent vertebral endplates,or to provide a desired disc space height between the vertebralendplates when head 32 is inserted into disc space 18 with first andsecond vertebral endplate surfaces 46, 48 adjacent respective ones ofthe vertebral endplates. It is contemplated that distractor 30 could beany one of a number of distracters provided in a kit in which thedistracters have heads of differing heights so that the distractorcorresponding to or providing the proper disc space height can beselected. It is further contemplated that head 32 can benon-distracting, and is positioned in the disc space to facilitatepositioning of instruments in the desired operative location relative todisc space 18, as discussed below.

Shaft 34 includes a proximal portion 41 and a distal portion 43separated by an offset portion 40. Proximal portion 41 includes a firstshaft portion 38 extending proximally from offset portion 40 along anaxis 39. A handle 36 extends from first shaft portion 38 and is orientedtransversely to axis 39. Distal portion 43 includes a guide portion 42extending distally from offset portion 40 along an axis 44. Head 32extends distally from guide portion 42. As discussed further below,guide portion 42 can be adapted to guide placement of a housingtherealong to a position adjacent disc space 18 when head 32 ispositioned in the disc space.

As shown further in FIG. 3, offset portion 40 is angled to positionproximal portion 41 anteriorly of distal portion 43 when distractor 30is operatively positioned in an anterior lateral approach to the discspace. Distal portion 43 can thus be positioned in the disc spaceposteriorly to avoid the major vessel and other structures along theanterior portion of the spinal column segment. Longitudinal axis 39 isoffset anteriorly by a distance 31 from longitudinal axis 44. It iscontemplated that offset distance 31 is sufficient so that with head 32positioned in the spinal disc in its operative anterior lateralorientation, distal portion 43 extends along longitudinal axis 44 fromthe disc space and proximal portion 41 is offset anteriorly to avoid theiliac crest. In the operative position, handle 36 extends anteriorly toprovide additional room for access and placement of surgical instrumentsalong the posterior side of distractor 30.

In one embodiment, offset portion 40 is spaced proximally about 60millimeters from the trailing end of distraction head 32, and offsetdistance 31 is about 20 millimeters. Other suitable dimensions andoffsets are also contemplated so that proximal portion avoids the iliaccrest when distractor 30 is inserted in an anterior-lateral approach tothe disc space.

In FIG. 4 there is shown a housing 50 comprising a frame portion 52including a posterior side wall 53 and an anterior side wall 55connected by an upper wall 62 and a lower wall 66. Walls 53, 55, 62, 66define an opening 54 through which in the operative position of housing50 instruments and implants can be inserted into the spinal disc space.Opening 54 is shown with a rectangular shape. Also contemplated is asquare shape or other suitable shape. Frame portion 52 includes aposterior extension 56 extending from posterior side wall 53 and ananterior extension 57 extending from anterior side wall 55. Posteriorextension 56 can be provided with a length greater than that of anteriorextension 57 such that posterior extension 56 extends substantiallyacross disc space 18 to protect the posterior portion of the spinalcolumn from intrusion by surgical instruments and implants during thesurgical procedure and to maintain disc space distraction. Anteriorextension 57 has a length sufficient to extend into the disc space tocontact the cortical rim to assist posterior extension 56 in maintainingspacing of the adjacent vertebrae during the surgical procedure. It isfurther contemplated that the length of anterior extension 57 does notextend into the implant insertion location in the anterior portion ofthe disc space and, as discussed further below, allows a spinal implantto be positioned at least in part anteriorly thereof. Other embodimentscontemplate an anterior extension 57 that extends across all or part ofthe disc space.

Upper wall 64 of frame portion 52 includes an upper slot 58 formedtherethrough and lower wall 66 includes a lower slot 60 formedtherethrough. Slots 58, 60 facilitate coupling of housing 50 to aninstrument, such as shaft assembly 126 discussed further below, so thatthe shaft assembly can remove housing 50 from the disc space. Upper wall62 includes a leading end 64 curved to conform to the curvature of thevertebral body against which it is positioned in the operative positionof housing 50. Similarly, lower wall 66 includes a leading end 68 curvedto conform to the curvature of the vertebral body against which it ispositioned in the operative position of housing 50. A proximally-openingnotch 70 is provided in posterior wall 53.

In FIGS. 5 and 6 there is shown a guide instrument 80 in perspective andside elevational views, respectively. Guide instrument 80 includes aproximal handle 82, a shaft 84 extending distally from handle 82, and aguide member 86 at the distal end of shaft 84. Guide member 86 includesa passage 90. Shaft 84 includes a distal portion 89, a proximal portion91, and an offset portion 87 therebetween. Distal portion 89 extendsalong an axis 81, offset portion 87 extends along an axis 83, andproximal portion 91 extends along an axis 95. Axis 95 and axis 81 can begenerally parallel to one another. Axis 83 forms an angle 85 with axis81 and axis 95.

As shown in further detail in FIG. 7, distal portion 89 is offset frompassage 90 so that distal portion 89 of shaft 84 can extend adjacent toguide portion 42 of shaft 34 of distractor 30 as guide member 86 ismoved along guide portion 42. In the illustrated embodiment, distalportion 89 is offset posteriorly from passage 90 in the operativeanterior lateral orientation so that shaft 84 extends along theposterior side of shaft 34 of distractor 30 in side-by-side relation. Asguide instrument 80 is inserted to the disc space in an anterior lateralapproach, angle 85 offsets proximal portion 91 cephaladly to avoid theiliac crest. Offset portion 87 can be further configured relative todistal portion 89 to offset proximal portion 91 anteriorly by a distance31, such as discussed above with respect to distractor 30. In oneembodiment, angle 85 is about 30 degrees. Other embodiments contemplatedangles 85 up to 90 degrees so long as proximal portion 91 avoids theiliac crest when positioned in an anterior lateral approach.

Guide member 86 includes a body 88 defining guide passage 90 extendingbetween a distal end and a proximal end of body 88. Tapered surfaces 92provide an opening into passage 90 along one side of body 88. Guidepassage 90 is sized to receive guide portion 42 of distractor 30 thereinin close-fitting and sliding engagement to permit controlled relativemovement of guide member 86 along guide portion 42. Body 88 includes adistal portion 96 and a proximal portion 98. Proximal portion 98includes a flanged wall 99 extending about and forming a lip aboutdistal portion 96. Distal portion 96 is sized for positioning in opening54 of housing 50 with flanged wall 99 in abutting engagement with theproximal end of housing 50.

In FIG. 8, a housing insertion instrument assembly 100 is provided thatincludes distractor 30, housing 50 and guide instrument 80. Guide member86 is positioned in opening 54 of housing 50 with protrusion 94 receivedin receptacle 70 and flanged wall 99 in abutting engagement with theproximal end of housing 50. With distractor 50 positioned in the desiredposition in disc space 18, offset portion 40 is configured so thatproximal portion 41 is positioned away from the iliac crest to providespace to receive guide instrument 80 and housing 50 therebetween.

Shaft 34 of distractor 30 is positioned in passage 90 of guide member 86proximal of guide portion 42. Guide member 86 and housing 50 areadvanced to position guide portion 42 in passage 90. Guide portion 42can have a cross-section enlarged relative to the proximal portion ofshaft 34 for sliding engagement with passage 90. It is contemplated thatpassage 90 of guide member 86 can be keyed to guide portion 42 toprevent rotation of guide instrument 80 thereabout and to ensure theproper orientation of housing 50 as it is guided to the disc space.Circular cross-sections are also contemplated. Housing 50 is guidedalong guide portion 42 to position frame 52 adjacent the L4 and L5vertebrae, and to position posterior extension 56 and anterior extension57 in the disc space. With housing 50 in its proper position relative todisc space 18, distractor 30 and guide instrument 80 are removedproximally from housing 50 with housing 50 remaining at the operativesite. Opening 54 of housing 50 provides access to the disc space forremoval of disc material, endplate preparation and implant insertion. Itis also contemplated that disc material removal, endplate preparationand other pre-implant insertion procedures can be conducted prior topositioning of housing 50.

Referring to FIG. 9, there is shown a partition member 110 having a body114 and a central extension 112 extending distally from body 114. Body114 includes an upper flange member 116 and a lower flange member 118extending from and transversely oriented to body 114. A mounting member122 extends transversely to and, in the operative anterior lateralorientation, cephaladly from upper flange member 116. Mounting member122 includes a slot 124 to facilitate attachment to an insertioninstrument. A slot 120 in body 114 is provided for engagement by a shaftassembly to facilitate withdrawal and manipulation of partition member110 relative to housing 50.

In FIG. 10 there is shown an implant insertion instrument assembly 200including housing 50 and partition member 110. Partition member 110 isremovably mounted to the distal end of a shaft 126 assembly. A proximalhandle 128 is provided at the proximal end of an inner shaft 130, and adistal handle 129 is coupled to an outer shaft 131. As shown in FIG. 11,the distal end of inner shaft 130 can include an engagement member 133that includes a distal extension 135 and a hook member 137 extendingfrom and transversely oriented to distal extension 135. Hook member 137can be positioned in slot 124 of mounting member 122, and outer shaft131 can be moved distally relative to inner shaft 130 to secure mountingmember 122 in a distally opening receptacle in outer shaft 131 such asslot 139. It is contemplated that outer shaft 131 can be threadinglycoupled to inner shaft 130, or that outer shaft 131 can be spring-biaseddistally relative to inner shaft 130. Movement of outer shaft 131 andinner shaft 130 relative to one another can remove mounting member 122from slot 139 and allow hook member 137 to be withdrawn from slot 124 ofmounting member 122.

Partition member 110 can be attached to shaft assembly 126 andpositioned through opening 54 of housing 50 so that central extension112 extends into the disc space between posterior extension 56 andanterior extension 57. When inserted through opening 54 of housing 50,upper flange member 116 is positioned along upper wall 62, and lowerflange member 118 is positioned along lower wall 66. Mounting member 122extends upwardly from upper wall 62 so that shaft assembly 126 islocated above the iliac crest at its proximal end when secured tomounting member 122. Spacing 132 between the flange members 116, 118 andbody 114 can be provided to receive the thickness of the upper and lowerwalls 62, 66 for sliding engagement therewith as partition member 110 ismoved relative to housing 50. Upper and lower walls 62, 66 can beparallel to one another to facilitate the sliding movement of partitionmember 100 therealong.

In FIG. 12 there is shown a wedge displacer instrument 140 comprising ahandle 142 and a shaft 144 extending distally from handle 142. Shaft 144includes an offset portion 146 separating shaft 144 into a proximalportion 147 and a distal portion 148. Distal portion 148 can extendgenerally parallel to proximal portion 147. A displacer wedge 150extends distally from distal portion 148 of shaft 144. Displacer wedge150 includes a lead end 152 and a trailing end 154. A first lateralsurface 158 and a second lateral surface 160 extend from leading end 152to trailing end 154 between a first surface 159 and an opposite secondsurface 161. Surfaces 158, 160 and ends 152, 154 form a wedge shape suchthat leading end 152 has a reduced width relative to trailing end 154.The reduced width leading end 152 facilitates insertion of displacerwedge 150 between posterior extension 56 of housing 50 and partitionmember 110. A bore 156 can be formed between first and second surfaces159, 161 of displacer wedge 150 to reduce the weight of displacer wedge150, although a solid displacer wedge 150 is also contemplated.

In FIG. 13 there is shown a second displacer instrument 170 comprising ahandle 172 and a shaft 174 extending distally from handle 172. Shaft 174includes an offset portion 176 separating shaft 174 into a proximalportion 177 and a distal portion 178. Distal portion 178 can extendgenerally parallel to proximal portion 176. A displacer head 180 extendsdistally from distal portion 178 of shaft 174. Displacer head 80includes a lead end 182 and a trailing end 184. A first lateral surface188 and a second lateral surface 190 extend from leading end 182 totrailing end 184 between a first surface 189 and an opposite secondsurface 191. Surfaces 188, 190 and ends 182, 184 form a box shape suchthat leading end 182 has the same width as trailing end 184. Othershapes are also contemplated so long as leading end 182 provides thedesired displacement of the implant at the distal end of partitionmember 110. A bore 186 is formed between first and second surfaces 189,191 of displacer head 180 to reduce the weight of displacer head 180,although a solid displacer head 180 is also contemplated.

In use, displacer wedge 150 of wedge displacer instrument wedge 140 canbe been inserted between partition member 110 and posterior extension 56of housing 50 to provide an initial separation. With wedge displacerinstrument 140 removed, second displacer instrument 170 is positionedwith leading end 182 of displacer head 180 between posterior extension56 of housing 50 and partition member 110. Leading end 182 can provide aseparation between the distal ends of posterior extension 56 andpartition member 110 that corresponds to the width of leading end 182.

With reference to FIGS. 14-19, a surgical procedure will be describedfor positioning a pair of interbody implants in spinal disc space 18through an anterior lateral approach with the instruments discussedabove. In FIG. 14 housing insertion instrument assembly 100 includesdistractor 30 with distractor head 32 positioned at the desired locationin disc space 18. The location of head 32 can be confirmed withfluoroscopy or other suitable viewing system. It is contemplated thathead 32 will be located centrally in disc space 18 and extend in themedial-lateral direction in its final orientation, although other finalorientations are contemplated. Shaft 34 of distractor 30 extends fromdisc space 18 laterally, and shaft 34 is offset anteriorly to avoid theiliac crest, as discussed above.

Housing 50 is mounted to guide member 86 of guide instrument 80 and thenpositioned about shaft 34 of distractor 30. Guide member 86 and thushousing 50 are guided along guide portion 42 to position posteriorextension 56 laterally along the posterior portion P of disc space 18and anterior extension 57 laterally along the anterior portion A of discspace 18. Frame 52 is positioned adjacent the vertebrae 14, 16 outsidedisc space 18 so that opening 54 can provide access to disc space 18while extensions 56, 57 maintain disc space distraction.

Referring now to FIG. 15, distractor 30 and guide instrument 80 areremoved from housing 50. Mounting member 122 of partition member 110 isattached to shaft assembly 126. Since mounting member 122 extendscephaladly from housing 50, shaft assembly 126 is positioned cephaladlyof the iliac crest as partition member 110 is inserted through opening54 of housing 50. Shaft assembly 126 is manipulated to positionpartition member 110 through opening 54 of housing 50 so that centralextension 112 extends into the disc space between posterior extension 56and anterior extension 57. Body 114 of partition member 110 is receivedin frame portion 52 with upper flange 116 and lower flange 118positioned along upper wall 62 and lower wall 66, respectively, to guidepartition 110 as it is moved relative to housing 50. Partition member110 is positioned as close as possible to posterior extension 56 tomaximize the space anteriorly of partition member 110 through opening 54for positioning of an implant therethrough. With partition member 110secured in housing 50, shaft assembly 126 can be uncoupled frompartition member 110.

In FIG. 16 an implant 250 is removably attached or engaged to the distalend of an implant inserter 300. Implant 250 is positioned in disc space18 between anterior extension 57 of housing 50 and central extension 112of partition member 110. Implant inserter 300 is detached from implant250, and, as shown in FIG. 17, wedge displacer instrument 140 ispositioned so that leading end 152 of displacer wedge 150 is locatedbetween partition member 110 and posterior extension 56. A lever, ifnecessary, can be inserted between housing 50 and partition member 110to provide an initial separation prior to insertion of displacer wedge150. Wedge displacer instrument 140 is advanced distally until trailingend 154 is positioned between frame 50 and partition member 110, therebymoving partition member 110 and implant 250 anteriorly in disc space 18and also anteriorly relative to housing 50.

Tapered leading end 152 of wedge displacer instrument 140 may notposition central extension 112 and implant 250 anteriorly far enough sothat implant 250 extends in a medial-lateral orientation in disc space18, particularly at the distal end of central extension 112. In FIG. 18,second displacer instrument 170 is positioned into opening 54 betweenposterior extension 56 and partition member 110 and advanced distally tomove at least the distal end of central extension 112 and thus implant250 anteriorly in disc space 18 and to align implant 250 in amedial-lateral orientation. In its medial-lateral position, it iscontemplated that implant 250 can be located in disc space 18 adjacentanterior extension 57. It is further contemplated that implant 250 canbe displaced anteriorly so that is located in whole or in partanteriorly of anterior extension 57. Thus, the present invention providepositioning of the implant in the anterior portion of the spinal discspace while avoiding the major vessel and other anatomical structuresalong the anterior portion of the spinal column.

With implant 250 in a desired position in disc space 18, partitionmember 110 can be removed by, for example, attaching shaft assembly 126thereto and withdrawing partition member 110 from disc space 18 andhousing 50. In FIG. 17, a second implant 270 is positioned in disc space18 through opening 54 of housing 50 in a medial-lateral orientationalong a posterior side of first implant 250.

The instruments and methods of the present invention facilitateplacement of implants 250, 270 in disc space 18 in a medial lateralorientation to provide bilateral support of the adjacent vertebrae 14,16 in the anterior and posterior areas of disc space 18. It is furthercontemplated that only a single implant may be inserted in disc space18. Bone graft, bone growth inducing material, and/or therapeutic agentscan be positioned in, around or integrated into the one or more implantspositioned in disc space 18. It is further contemplated that the one ormore implants positioned in disc space 18 can be fusion devices, bonesupport devices, artificial disc devices, or other suitable device forimplantation between vertebrae. The one or more implants can be providedwith an outer surface structure to engage the vertebral endplates, andone or more chambers, cavities and/or recesses for receiving bone growthmaterial. The one or more implants can also be flexible, or include oneor more articulating components, to provide segmental motion between theadjacent vertebrae.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. All changes,modifications and equivalents that come within the spirit of theinvention as defined by the following claims are desired to be protected

1. A surgical instrument insertable in a spinal disc space between anupper vertebra and a lower vertebra, comprising: a head including anupper surface positionable adjacent an endplate of the upper vertebraand an opposite lower surface positionable adjacent an endplate of thelower vertebra; and a shaft extending proximally from said head, saidshaft including a distal portion, a proximal portion, and an offsetportion therebetween, said distal portion including a guide portionadjacent said head and engageable to guide an instrument therealong tothe spinal disc space, said head and said guide portion extending alonga first axis and said offset portion extending proximally from saidguide portion and transversely oriented thereto.
 2. The instrument ofclaim 1, wherein said proximal portion extends along a second axisgenerally parallel to said first axis.
 3. The instrument of claim 2,wherein said proximal portion includes a handle oriented transversely tosaid second axis.
 4. The instrument of claim 2, wherein said offsetportion extends along a third axis oriented at an angle to said firstaxis.
 5. The instrument of claim 1, wherein said guide portion includesa cross-sectional dimension along a length thereof that is greater thana cross-sectional dimension along a length of said proximal portion. 6.A surgical instrument for spinal surgery having an operative orientationincluding an anterior lateral approach to a spinal disc space between L4and L5 vertebrae of a patient, comprising: a distal end portionpositionable adjacent the spinal disc space and a proximal portionoffset from said distal portion to avoid an iliac crest of the patientwhen the surgical instrument is the operative orientation.
 7. Theinstrument of claim 6, wherein the instrument is a distractor includinga head at said distal portion positionable in the spinal disc space andsaid proximal portion includes a shaft extending distally from saidhead, said proximal portion being offset anteriorly of the iliac crestin the operative orientation.
 8. The instrument of claim 6, wherein theinstrument is a guide instrument including a guide member at said distalportion and said proximal portion includes a shaft extending distallyfrom said head, said proximal portion being offset cephaladly of theiliac crest in the operative orientation.
 9. A surgical instrumentassembly for providing access to a spinal disc space, comprising: adistractor including a head positionable in a spinal disc space and ashaft extending proximally from said head, said shaft including a guideportion along at least a portion thereof adjacent said head; a housingincluding an opening therethrough for providing access to the spinaldisc space when positioned adjacent thereto; and a guide instrumentincluding a shaft and a guide member at a distal end of said shaft, saidguide member removably engaged to said housing, said guide membermoveable along said guide portion of said distractor with said shaft ofsaid guide instrument in side-by-side relation to said shaft of saiddistractor to guide said housing along said distractor to the spinaldisc space when said head is positioned in the spinal disc space. 10.The assembly of claim 9, wherein said housing includes a frame portiondefining said opening therethrough, said housing further including afirst extension along one side of said opening extending distally fromsaid frame portion and a second extension along an opposite side of saidopening extending distally from said frame portion, said first andsecond extensions positionable in the spinal disc space to maintain adisc space distraction when said head is removed from the spinal discspace.
 11. The assembly of claim 10, wherein said first extension islonger than said second extension.
 12. The assembly of claim 10, whereinsaid frame portion includes an upper wall positionable adjacent an uppervertebra and a lower wall positionable adjacent a lower vertebra, saidupper and lower walls each including a distal end curvaturecorresponding to a curvature of a lateral profile of the upper and lowervertebrae, respectively.
 13. The assembly of claim 9, wherein saidopening includes a rectangular shape.
 14. The assembly of claim 9,wherein said guide member includes a distal portion positionable in saidopening to engage said guide member in said opening and a proximalportion forming a lip around said distal portion, said lip in abuttingengagement with a proximal end of said housing when said distal portionis positioned in said opening.
 15. The assembly of claim 14, whereinsaid housing includes a proximally-opening notch in a wall thereof andsaid guide member includes a protrusion positionable in said notch. 16.The assembly of claim 9, wherein said guide member includes a passageextending between a distal end and a proximal end of said guide memberand said guide portion of said distractor is movably received in saidpassage.
 17. The assembly of claim 16, wherein said guide memberincludes tapered surfaces forming an opening into said passage along oneside thereof.
 18. The assembly of claim 16, wherein said passage extendsalong a center of said guide member and said shaft of said guideinstrument is offset from said passage.
 19. The assembly of claim 18,wherein said shaft of said guide instrument includes a distal portion, aproximal portion, and an offset portion therebetween, said offsetportion positioning said proximal portion cephaladly of said distalportion in an operative orientation of said guide instrument.
 20. Theassembly of claim 18, wherein said shaft is offset posteriorly of saidpassage in said operative orientation of said guide instrument.
 21. Theassembly of claim 9, wherein said shaft of said distractor includes adistal portion, a proximal portion, and an offset portion therebetween,said distal portion including said guide portion, said head and saidguide portion extending along a first axis and said offset portionextending proximally from said guide portion along a second axisoriented at a first angle relative to said first axis.
 22. The assemblyof claim 21, wherein said proximal portion extends along a third axisgenerally parallel to said first axis.
 23. The instrument of claim 22,wherein said proximal portion includes a handle oriented transversely tosaid third axis.
 24. The instrument of claim 21, wherein said guideportion includes a cross-sectional dimension along a length thereof thatis greater than a cross-sectional dimension along a length of saidproximal portion. 25-56. (canceled)